This invention concerns a method for the feeding of long pieces of wood into a disc chipper against a disc equipped with blades, rotating around a horizontal axis, in such a way that the piece of wood encounters the bladed disc at a sharp input angle, whereupon the sharp input angle (or the angle between the direction of the piece of wood and the plane of the disc, the angle of the piece and wood perpendicular to the plane of the disc) is achieved by combining with the sharp inclination of the piece of wood the angle around the axis of the disc, i.e. combining with the projection of the angle at the plane of the disc between the direction of the piece of wood and the horizontal direction, a sharp angle of rotation around the vertical axis, i.e. the projection on the horizontal level of the angle between the piece of wood and the plane of the disc. The invention also concerns a disc chipper for the chipping of long pieces of wood, in which the chipper has a disc rotating about a horizontal axis, equipped with blades and with an inclined chute feeder, in which the angle between the chute feeder and the blade disc is sharp, whereupon the sharp angle between the chute feeder and the plane of the disc, perpendicular to the plane of the disc and in the direction of the chute, is formed by combining with the sharp angle of inclination of the chute feeder around the axis of the chute, i.e. the angle between the direction of the chute and the horizontal direction, a projection on the level of the disc around the vertical axis of the sharp angle of rotation around the vertical axis, i.e. with a projection on the horizontal plane of the angle between the chute feeder and the plane of the disc.
The forest industries today commonly use disc chippers to chip wood before further processing. One disc chipper is described in Finnish patent 79799.
When wood is fed in, it encounters the blade disc at an input angle, which is achieved with a horizontally fed chipper by the angle on the horizontal plane between the feeder conveyor and the blade disc, or on a chute fed chipper by the angle of inclination on the vertical plane of the chute. Tests indicate that the chip quality is improved when the input angle between the wood and the blade disc is narrowed.
On a horizontal feed chipper, it is easy to do this, since the change in the angle is done at ground level. The problem with a horizontal feed chipper, however, is that short pieces of wood cannot be fed against the chipper, since a horizontal conveyor cannot be built against the blade disc.
It is difficult to build a steep chute for a chute chipper, as is the feeding of wood. Furthermore, a steep chute results in an irregular feed and feeding at a high feed force. Today there are chute fed chippers on the market which achieve a reasonable chute input angle between a small piece of wood and the blade disc by inclining the axis of the blade disc. The problem with this structure is that all parts have to be installed on a sloping surface.